Electric power systems have multiple generation units that operate in synchronism under a normal operation. That is, frequency, phase, and amplitude of voltages at the terminals of a generator hold a fixed relationship with the same parameters of the remaining generators in the power system. Before a generator can be connected to an electric power system, the frequency, phase, and amplitude of the voltages at its bus need to be matched with those of the power system at the point of interconnection. Once, the so called synchronization parameters are matched within a desired tolerance, the generator breaker is closed. Any mismatch in the synchronization parameters during connection of a generation unit by a generator breaker may result in undesired transients and disruption of the system.
The concept of microgrid, in which several small distributed generation units operate together to form a small power system, is finding increasing acceptance as a solution to increase the share of renewable energy resources. A microgrid may be operated in either of the following two modes: grid-connected mode and islanded mode. In grid-connected model, entire microgrid constituting several distributed generation units operate as a single generator from the perspective of the main grid. Hence, synchronization of a microgrid with the main grid is further challenging as the synchronization parameters of the microgrid at the point of interconnection with the main grid depends on several generation units. Synchronization process may also require communication among the distributed generation units in the microgrid.
U.S. Pat. No. 7,122,916 B2 discloses a multi-unit power generation system comprising a plurality of generators connected in parallel, a switching system for switching between and/or aggregating a generator load produced by the plurality of generators and a utility grid load, and a control system. The control system is in communication with each generator for communicating command signals to each generator. The control system is further in communication with the switching system for commanding the switching system to switch between or aggregate the generator load and the utility grid load. Each generator may comprise, for example, a micro-turbine generator.